Exhaust device for work vehicle

ABSTRACT

A curved-pipe portion curved so as to change the exhaust direction is provided to the downstream-side end section of the exhaust guide pipe and the external protective pipe, and the spacing between an end-section outer periphery of the exhaust guide pipe and an end-section inner periphery of the external protective pipe in the curved-pipe portion is configured so as to be greater on the side opposite the center of curvature of the curved-pipe portion than the side nearer thereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exhaust device for a work vehicleprovided with an exhaust pipe for guiding exhaust to the exterior of thevehicle body.

2. Description of the Related Art

Known exhaust devices for a work vehicle such as that mentioned aboveinclude the following.

Specifically, Japanese Patent 3799405 discloses the following exhaustdevice for a work vehicle. Specifically, this exhaust device for a workvehicle is configured so that: an insulating pipe is externally fittedon the outside of an exhaust guide pipe into which exhaust from anengine is introduced; a cooling pipe is externally fitted in turn on theoutside of the insulating pipe; heat in the innermost exhaust guide pipeis insulated by the insulating pipe at an intermediate position; andexternal air entering in a gap with respect to the outermost coolingpipe having a vent hole positioned on the outside of the insulating pipecools the insulating pipe and prevents exhaust heat from beingtransmitted to the outside of the cooling pipe (e.g., see paragraphs0016, 0025 and FIGS. 2, 3, and 13).

JP-A 07-71249 discloses the following exhaust device for a work vehicle.Specifically, this exhaust device for a work vehicle is configured sothat: an exhaust guide pipe into which exhaust from the engine isintroduced comprises an upstream-side guide pipe and a downstream-sideguide pipe located to the front and to the rear in the direction ofexhaust flow; and an ejector section provided between the upstream-sideguide pipe and the downstream-side guide pipe causes external air to mixwith the exhaust in the downstream-side guide pipe by means of anejector effect accompanying the inflow of exhaust from the upstream-sideguide pipe to the downstream-side guide pipe. The outside of thedownstream-side guide pipe is covered by an external protective pipe forinsulation (e.g., paragraphs 0020, 0028, FIGS. 4, 5, and 6).

SUMMARY OF THE INVENTION

In the structure set forth in Japanese Patent 3799405, the exhaust pipeis configured from a three-layer structure in which an insulating pipeand a cooling pipe are externally fitted on the outside of an exhaustguide pipe into which exhaust from the engine is introduced; therefore,a problem is presented in that the exhaust pipe is likely to be alarge-size pipe having a large diameter. There is a demand for a compactconfiguration in which an increase in the size of the exhaust pipe isavoided.

According to the structure set forth in JP-A 07-71249, external air ismixed using an ejector effect into the exhaust in the downstream-sideguide pipe, whereby the exhaust temperature in the downstream-side guidepipe is reduced, and the outside of the downstream-side guide pipe iscovered by an external protective pipe for insulation so that theoutside of the exhaust pipe is prevented from overheating.

In this structure, external air sucked in by the ejector section entersthe inside of the downstream-side guide pipe, and flows in a state ofmixing with the exhaust. Therefore, even though the admixing of externalair lowers the exhaust temperature to a certain extent, the temperatureof the downstream-side guide pipe, which comes into contact with theexhaust, is substantially high; therefore, it is necessary to providethe external protective pipe for insulation at a position significantlydistant from the outer periphery of the downstream-side guide pipe, andit is difficult to sufficiently reduce the diameter of the exhaust pipe.

Also, in an ejector section having this configuration, in order to blowthe exhaust out from the terminal end of the downstream-side guide pipetowards a predetermined direction, the terminal end section of theupstream-side guide pipe is narrowed to increase the flow speed of theexhaust where the external air is drawn in. Therefore, pressure loss isgenerated at this location, resulting in a corresponding energy loss.

With the above-mentioned in view, there is a demand for an exhaustdevice for a work vehicle having a structure in which an exhaust pipe inwhich the outside can be prevented from overheating has a compactconfiguration, external air can be suctioned by an ejector effect in anefficient manner, and high-temperature exhaust can be readily dischargedwithout difficulty.

An exhaust device for a work vehicle according to the present inventioncomprising: an exhaust pipe for guiding exhaust to a vehicle exterior,the exhaust pipe including: an exhaust guide pipe into which exhaustfrom an engine is introduced; an external protective pipe thatexternally fits onto the exhaust guide pipe and forms a passage forexternal air in a space bounded on one side by the exhaust pipe; and anejector section for suctioning and introducing external air between anouter periphery of the exhaust guide pipe and an inner periphery of theexternal protective pipe by an ejector effect caused by exhaustdischarged from the exhaust guide pipe, the ejector section being formedon a downstream-side end section of the exhaust pipe by positioning adownstream-side end section of the external protective pipe furtherdownstream, with respect to an exhaust direction, than a downstream-sideend section of the exhaust guide pipe; wherein a curved-pipe portioncurved so as to change the exhaust direction is provided to thedownstream-side end section of the exhaust guide pipe and the externalprotective pipe, and the spacing between an end-section outer peripheryof the exhaust guide pipe and an end-section inner periphery of theexternal protective pipe in the curved-pipe portion is configured so asto be greater on the side opposite the center of curvature of thecurved-pipe portion than the side nearer thereto.

According this configuration, the downstream-side end section of theexternal protective pipe is positioned further downstream, with respectto the exhaust direction, than the downstream-side end section of theexhaust guide pipe; the ejector section is provided to thedownstream-side end section of the exhaust pipe; and external air issuctioned and introduced between the outer periphery of the exhaustguide pipe and the inner periphery of the external protective pipe.Therefore, the external air can be discharged from the downstream-sideend section of the exhaust guide pipe while the external air is made toflow between the outer periphery of the exhaust guide pipe and the innerperiphery of the external protective pipe.

Therefore, compared to a structure merely comprising a gap between theouter periphery of the exhaust guide pipe and the inner periphery of theexternal protective pipe, and lacking active flow of external air, it ispossible to cause the external air to move in an active manner betweenthe outer periphery of the exhaust guide pipe and the inner periphery ofthe external protective pipe, and efficiently minimize the transmissionof heat from the exhaust guide pipe to the external protective pipe. Asa result, it also becomes possible to narrow the spacing between theexhaust guide pipe and the external protective pipe, reduce the diameterof the entire exhaust pipe, and obtain a compact configuration.

Also, the ejector section allows the flow of exhaust discharged directlyfrom the engine to be used as an ejector, in contrast to a structurethat produces a loss in pressure, such as that in which a part of theexhaust guide pipe is narrowed and external air is drawn in while theflow speed is increased.

In other words, the downstream-side end section of the externalprotective pipe is positioned further downstream, with respect to theexhaust direction, than the downstream-side end section of the exhaustguide pipe, whereby a configuration is obtained in which external airpresent in the pathway between the exhaust guide pipe and the externalprotective pipe is more susceptible to being drawn into the flow ofexhaust discharged from the downstream-side end section of the exhaustguide pipe; therefore, external air can be taken in without any pressureloss caused by narrowing, and it becomes possible to suction externalair in an efficient manner that avoids energy loss caused by pressureloss.

The downstream-side end section of the exhaust guide pipe and theexternal protective pipe comprises a curved-pipe portion that is curvedso as to change the exhaust direction, allowing the direction in whichthe exhaust is discharged to be changed. However, if, as describedabove, the downstream-side end section of the external protective pipeis positioned further downstream, with respect to the exhaust direction,than the downstream-side end section of the exhaust guide pipe, there isa risk of high-temperature exhaust discharged from the downstream-sideend section of the exhaust guide pipe coming into localized contact withthe downstream-side end section of the external protective pipepositioned further downstream, with respect to the exhaust direction,than the downstream-side end section of the exhaust guide pipe; and of[the high-temperature exhaust] causing burn damage on thedownstream-side end section of the external protective pipe.

Therefore, according to the present invention, taking into account thefact that the flow inertia of the exhaust before reaching thecurved-pipe portion has a tendency of acting to turn the flow directionof the exhaust away from the center of curvature of the curved-pipeportion, the spacing between the outer periphery of the end section ofthe exhaust guide pipe and the inner periphery of the end section of theexternal protective pipe in the curved-pipe portion is [configured] soas to be greater on the side opposite the center of curvature of thecurved-pipe portion than on the side nearer the center of curvature ofthe curved-pipe portion. The possibility of the exhaust discharged fromthe downstream-side end section of the exhaust guide pipe coming intocontact with the downstream-side end section of the external protectivepipe is thereby reduced.

With regards to the above configuration, a terminal-end opening on thedownstream-side of the exhaust guide pipe and a terminal-end opening onthe downstream-side of the external protective pipe are preferablyprovided so that, when viewed along the exhaust direction from theterminal-end opening, a center point of the terminal-end opening of theexhaust guide pipe is positioned nearer the center of curvature of thecurved-pipe portion than the center point of the terminal-end opening ofthe external protective pipe.

According to this configuration, the spacing between an end-sectionouter periphery of the exhaust guide pipe and an end-section innerperiphery of the external protective pipe in the curved-pipe portion isconfigured so as to be greater on the side opposite the center ofcurvature of the curved-pipe portion than the side nearer thereto, andcan be set as expected while the respective cross-section profiles ofthe exhaust guide pipe and the external protective pipe are kept thesame.

Therefore, it is possible to avoid [the need for] a cumbersome procedureduring manufacture, such as varying the cross-section profile of theexhaust guide pipe or the external protective pipe to change thespacing.

With regards to the above configuration, the curved-pipe portion of theexhaust guide pipe and the external protective pipe is preferablyconfigured using a member that is separate from the external protectivepipe and the exhaust guide pipe positioned further upstream from thecurved-pipe portion.

According to the present configuration, it is possible to configure thecurved-pipe portion exposed to high-temperature exhaust using a separatemember having a higher heat resistance than the external protective pipepositioned upstream of the curved-pipe portion and enhance durability,or to allow the curved-pipe portion to be replaceable as a standaloneand increase durability in terms of cost.

With regards to the above configuration, a heat-resistant coating ispreferably applied to the curved-pipe portion of the exhaust guide pipeand the external protective pipe.

According to the above configuration, it is possible to increase theheat resistance of the curved-pipe portion exposed to high-temperatureexhaust in a relatively simple manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall side view of a tractor;

FIG. 2 is an overall front view of the tractor;

FIG. 3 is a perspective view of an exhaust device;

FIG. 4 is an exploded perspective view of the exhaust device;

FIG. 5A is a perspective view showing the installation location of aflow regulator;

FIG. 5B is a cross-sectional view along line Vb-Vb in FIG. 5A and apartially expanded view thereof;

FIG. 5C is a perspective view of the flow regulator;

FIG. 6 is a cross-sectional view along line VI-VI in FIG. 3;

FIG. 7A is a cross-sectional view along line VIIa-VIIa in FIG. 3 showingthe downstream-side exhaust pipe;

FIG. 7B is a cross-sectional view along line VIIb-VIIb in FIG. 3 showingthe downstream-side exhaust pipe;

FIG. 8 is a cross-sectional view along the vertical direction showingthe external air introduction section at the bending section;

FIG. 9A is a vertical cross-sectional view along the longitudinaldirection showing the downstream-side end section of the exhaust device;and

FIG. 9B is a cross-sectional view along line IXb-IXb in FIG. 9A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[Overall Configuration of Work Vehicle]

FIG. 1 shows an entire side surface of a tractor with a cabin, which isan example of a work vehicle to which the exhaust device according tothe present invention is applied. This tractor carries a mobility unit 1positioned at the front section of the vehicle body, and a driving cabin2, representing an occupant-carrying driving unit, positioned at therear section of the vehicle body, on a vehicle body frame 5 configuredby integrally linking an engine-carrying frame 3, a clutch housing (notshown), and a transmission case 4. The vehicle body frame 5 is supportedby a pair of left and right front wheels 6 and rear wheels 7.

In the mobility unit 1, an engine 8, which is a diesel engine supportedin a vibration-proofed manner by an anti-vibration material (not shown),is installed on the engine-carrying frame 3 in an engine compartmentcovered by an engine bonnet 1A. There is adopted a configuration suchthat the power from the engine 8 is transmitted to the front wheels 6and the rear wheels 7 through a travel transmission system comprising aspeed-change device for travelling (not shown) and other elementsinternally provided to the transmission case 4, which also functions as[a part of] the frame, and a four-wheel-drive tractor is obtained.

The rear section of the transmission case 4 is equipped with a pair ofleft and right lift arms 10 actuated by a hydraulic hoisting cylinder 9internally provided to the upper rear section of the rear section anddriven so as to be capable of swinging in the vertical direction, apower take-off (PTO) shaft 11 that allows the engine power to be drawnout to an outer part; and other components. The power from the engine 8is transmitted to the power take-off shaft 11 through a worktransmission system, which is a different system than the traveltransmission system internally provided to the transmission case 4 andwhich comprises a speed-change device for work (not shown), a workclutch (not shown), and other elements.

A link mechanism (not shown) provided in a linking manner to the rearsection of the transmission case 4 so as to be capable of swinging upand down is linked to the left and right lift arms 10. A transmissionshaft for relaying power to a rotary tiller or a similar implement (notshown) that is linked to the link mechanism, or a similar component isconnected to the power take-off shaft 11.

As shown in FIGS. 1 and 2, the driving cabin 2 is formed as arectangular box having a roof material 13 supported by cabin frames 12that are provided upright at front, rear, left, and right corners; afront surface glass panel 14 comprising a transparent curved-surfaceglass panel or another glass panel provided to the front side; and apair of outward-opening left and right door panels 15 made fromtransparent glass provided to the left and right side sections. Thedriving cabin 2 is provided with a steering wheel 16, a driving seat 17,and other elements in the interior.

[Exhaust Device]

An exhaust cleaning treatment device 20 with a muffler function isprovided in the engine bonnet 1A of the mobility unit 1 so as to bepositioned on the upper side of the engine 8, and is designed toaccommodate a diesel oxidation catalyst (DOC) and a diesel particulatefilter (DPF). The exhaust cleaning treatment device 20 is configured soas to treat the exhaust from the engine 8 and discharge the exhausttowards an exhaust pipe 21.

The exhaust cleaning treatment device 20 is configured so as to capturemicroparticulate substances contained in the exhaust using the DPF, andcause unburned fuel in the exhaust to oxidize and combust using the DOCto increase the temperature of the exhaust, thereby incinerating themicroparticulate substances captured by the DPF to perform recycling inthe DPF. As a result, a high-temperature exhaust gas flows in theexhaust pipe 21.

The exhaust pipe 21 is configured so as to comprise a cylindricalexhaust guide pipe 30 into which exhaust from the engine 8 isintroduced, and an external protective pipe 40 that externally fits ontoto the exhaust guide pipe 30 and forms a pathway r for allowing passageof external air, the pathway r being formed between the externalprotective pipe 40 and the outer periphery of the exhaust guide pipe 30.

The exhaust device of the present invention is configured from acombination of the above-mentioned exhaust cleaning treatment device 20and exhaust pipe 21.

[Exhaust Pipe]

As shown in FIGS. 3 and 4, the exhaust pipe 21 comprising the exhaustguide pipe 30 and the external protective pipe 40 has a bending section22 provided at an intermediate position, and is configured so as tochange the direction of exhaust gas discharge from the horizontaldirection to the vertical direction.

Specifically, the exhaust pipe 21 comprises an upstream-side exhaustpipe 23 positioned on the upstream side of the bending section 22, and adownstream-side exhaust pipe 24 positioned on the downstream side of thebending section 22. The upstream-side end section of the upstream-sideexhaust pipe 23 is connected to the exhaust cleaning treatment device20. Exhaust gas fed from the exhaust cleaning treatment device 20 isdischarged from an exhaust section 25 provided to the downstream-sideend section of the downstream-side exhaust pipe 24.

There is adopted a configuration in which external air to the pathway rof the exhaust pipe 21 is suctioned and introduced through an externalair introduction section 50 provided to a location corresponding to thebending section 22 that is positioned between the downstream-side endsection of the upstream-side exhaust pipe 23 and the upstream-side endsection of the downstream-side exhaust pipe 24, caused to pass throughthe pathway r between a downstream-side guide pipe 32 and adownstream-side protective pipe 42 described further below, anddischarged from the exhaust section 25 with the exhaust gas.

The upstream-side exhaust pipe 23 comprises an upstream-side guide pipe31 forming part of the exhaust guide pipe 30, and an upstream-sideprotective body 41 forming part of the external protective pipe 40. Thedownstream-side exhaust pipe 24 comprises the downstream-side guide pipe32 forming part of the exhaust guide pipe 30, and the downstream-sideprotective pipe 42 forming part of the external protective pipe 40. Thebending section 22 represents the location at which the upstream-sideguide pipe 31 and the downstream-side guide pipe 32 are connected.

The upstream-side exhaust pipe 23 is configured so as to comprise: theupstream-side guide pipe 31, the upstream side of which is connected tothe exhaust cleaning treatment device 20; and the channel-shapedupstream-side protective body 41 covering the upper side of theupstream-side guide pipe 31.

As shown in FIG. 4, the upstream-side guide pipe 31 is configured so asto comprise, between the bending section 22 and the exhaust cleaningtreatment device 20, a cylindrical portion 31 b having a substantiallyhorizontally oriented cylinder axial center x continuing onto thebending section 22; and a flexible tube 31 a positioned further upstreamof the horizontally oriented cylindrical portion, and designed so that alocation connecting to an exhaust pipe portion 20 a of the exhaustcleaning treatment device 20 can be flexed in any direction.

As shown in FIGS. 5A through 5C, flow-regulating plates 26 are providedat a location, in the exhaust pipe portion 20 a of the exhaust cleaningtreatment device 20, that is fitted into the upstream-side guide pipe 31and connected to the upstream-side guide pipe 31 by a constricting band(not shown). The flow-regulating plates 26 are attached so that in astate in which respective peak sections of two mountain-shaped platematerials 27 having peaks that are bent substantially at a right angleare caused to face each other in an opposing state and a state in whicha small spacing c is present between the peak sections, the foot of eachof the mountain-shaped plate materials 27 is welded and secured againstthe inner periphery side of the exhaust pipe portion 20 a; and so thatthe mountain-shaped plate materials 27 appear as a cross when viewedfrom the direction of the axial line of the pipe.

As shown in FIG. 5C, an upstream-side edge 27 a of each of theflow-regulating plates 26 is formed as an inclined edge tapered so as tobe positioned further towards the upstream side with increasingproximity to the center of the exhaust pipe portion 20 a in the radialdirection, so as to reduce contact resistance with respect to theexhaust gas.

The terminal end section of the exhaust pipe portion 20 a to which theflow-regulating plates 26 are attached is connected by being constrictedby a constricting band (not shown) from the outside of the upstream-sideguide pipe 31 in a state of being fitted into the starting end sectionof the upstream-side guide pipe 31. There is a tendency for the terminalend section of the exhaust pipe portion 20 a to slightly decrease indiameter by being constricted. However, even if the diameter of theterminal end section of the exhaust pipe portion 20 a has decreased indiameter, the spacing c is present between the peak sections of theflow-regulating plates 26, and the exhaust pipe portion 20 a cantherefore be reduced in diameter without difficulty by slightlydecreasing the width of the spacing c. Therefore, there is little riskof the exhaust pipe portion 20 a being deformed to a warped shape, therewill be few instances in which the exhaust pipe portion 20 a decreasesin diameter while deforming to a warped shape at the location of fittingwith the upstream-side guide pipe 31 so that a gap is generated boundedon one side by the upstream-side guide pipe, and anomalous events suchas leakage of the exhaust gas can be readily avoided.

Within the upstream-side exhaust pipe 23, the upstream-side protectivebody 41 formed to a channel shape has a sheet-shaped insulating material41 b attached by riveting to the inside of a channel-shaped outer cover41 a, the lower side of which is open, as shown in FIGS. 3, 4, and 6.The sheet-shaped insulating material 41 b is created by forming analuminum corrugated material, and has heat-proofing and sound-proofingfunctions.

The upstream-side protective body 41 is installed across a rangecovering: the substantially horizontally oriented cylindrical portion 31b continuing to the bending section 22; and the flexible tube 31 acontinuing to the horizontally oriented cylindrical portion 31 b, theflexible tube 31 a positioned on the outside of the engine bonnet 1A.

With regards to the upstream-side protective body 41, the open-end sideof a connecting piece 31 c, which is formed to a channel shape in planview, is secured by welding to the outer periphery section of the lowerhalf of the upstream-side guide pipe 31; and the other end of theconnecting piece 31 c is extended outward, in the horizontal direction,with respect to the outer periphery of the upstream-side guide pipe 31,and detachably linked and secured by a securing bolt 41 c in a state ofbeing held against the inner periphery side of the upstream-sideprotective body 41.

As shown in FIGS. 3, 4, 7A, and 7B, the downstream-side exhaust pipe 24is configured so as to comprise: the downstream-side guide pipe 32stretching from the bending section 22 to the exhaust section 25 of thedownstream-side end section; the downstream-side protective pipe 42(corresponding to the external protective pipe 40) covering the outerperiphery side of the downstream-side guide pipe 32; and a side-sectioncover 45.

The downstream-side guide pipe 32 is configured so as to comprise: acylindrical straight-pipe portion 32 a provided upright so as to have acylinder axial center y disposed in the vertical direction; and acurved-pipe portion 32 b that is positioned on the upper end section ofthe straight-pipe portion 32 a and that is curved so as to be orientedin a predetermined direction (front side).

The lower end section of the straight-pipe portion 32 a links to thebending section 22. The curved-pipe portion 32 b is provided to theupper end section of the straight-pipe portion 32 a. The upper end ofthe curved-pipe portion 32 b opens to the exterior and forms aterminal-end opening 32 c.

The downstream-side protective pipe 42 comprises a straight-pipe-shapedcover portion 42 a formed to a straight pipe shape so as to bepositioned on the outer periphery side of the straight-pipe portion 32 aof the downstream-side guide pipe 32, and a curved-pipe portion 42 bconnected to the upper end section of the straight-pipe-shaped coverportion 42 a.

The straight-pipe-shaped cover portion 42 a is formed so that a pair offront and rear half-cylindrical members 43, 43 form a cylindricalstraight pipe that stands upright along the cylinder axial center ydisposed in the vertical direction in a state in which split-surfaceedge portions of the half-cylindrical members 43 are positioned againsteach other. As shown in FIG. 7A, the half-cylindrical members 43, 43 arepositioned on the outside of channel-shaped attachment brackets 33, 33provided to the outer peripheral portion on left and right sides of thedownstream-side guide pipe 32, and linked and secured in a fastenedstate by linking bolts 34 in a state in which respective edges arepositioned against each other.

A sheet-shaped insulating material 44 is also attached by means ofriveting to the inner peripheral surface side of each of thehalf-cylindrical members 43, 43. However, in the sheet-shaped insulatingmaterial 44, the inner peripheral surface side that faces the externalair pathway r is formed as a relatively smooth surface in comparison tothe sheet-shaped insulating material 41 b provided to the inside of theouter cover 41 a of the upstream-side protective body 41.

Specifically, the sheet-shaped insulating material 41 b provided to theinside of the outer cover 41 a of the upstream-side protective body 41has an uneven shape on the inner surface side on the inner peripheryside of the outer cover 41 a, and has a structure in which insulatingand soundproofing functions are enhanced. In contrast, even though thesheet-shaped insulating material 44 on the inner peripheral surface sideof the half-cylindrical members 43, 43 is obtained by forming analuminum corrugated material, the sheet-shaped insulating material 44 isformed so that a relatively smooth surface having little unevenness ispresent on the inner peripheral surface side facing the pathway r. Thisis to prevent the flow of external air from the external airintroduction section 50 below to the exhaust section 25 above from beinginhibited.

As shown in FIG. 4, the pair of front and rear half-cylindrical members43, 43 forming the straight-pipe-shaped cover portion 42 a are alsodivided into two in the vertical direction. The half-cylindrical members43, 43 positioned at the lower section and the half-cylindrical members43, 43 positioned at the upper section are installed in a state in whichthe respective upper ends and lower ends face each other in an opposingstate in the cylinder axial center y-direction.

Each of the half-cylindrical members 43, 43 positioned at the lowersection and the half-cylindrical members 43, 43 positioned at the uppersection is linked and secured, in a fastened state, by linking bolts 34in a state in which respective edges are positioned against each other,to the channel-shaped attachment brackets 33, 33 provided to the outerperipheral portion on the left and right sides of the downstream-sideguide pipe 32, as described above.

The curved-pipe portion 42 b connected to the upper end section of thestraight-pipe-shaped cover portion 42 a is configured from an elbow pipethat is curved so that the lower-end side externally fits onto the upperend section of the straight-pipe-shaped cover portion 42 a, and theexhaust direction in the terminal-end opening 42 c formed on theupper-end side (see center lines p1, p2 in FIG. 9A) is orienteddiagonally upwards towards the front of the vehicle body.

The curved-pipe portion 42 b of the downstream-side protective pipe 42is positioned so as to enclose the outer periphery side of thecurved-pipe portion 32 b of the downstream-side guide pipe 32, isprovided with a heat-resistant coating applied to the inner peripheralsurface side so as to obtain a higher heat resistance than that of thestraight-pipe-shaped cover portion 42 a, and is detachably attached tothe upper end section of the straight-pipe-shaped cover portion 42 a bya linking bolt or other appropriate linking means (not shown).

The side-section cover 45 positioned on the outside, in the lateraldirection, of the straight-pipe-shaped cover portion 42 a comprises aseries of plate materials that have a gutter shape in which theopening-side spreads outwards in cross-section, as shown in FIGS. 3, 4,and 7B. The plate materials are positioned on the outside, in thelateral direction, of the location at which the edge portions on thesplit-surface side of the half-cylindrical members 43, 43 are positionedagainst each other; and extend from the upper end to the lower end ofthe straight-pipe-shaped cover portion 42 a so as to cover the locationat which the edge portions are positioned against each other.

The side-section cover 45 is linked and secured to thestraight-pipe-shaped cover portion 42 a by a separate linking bolt 46 ata location positioned differently in the vertical direction than thelocation at which the front and rear half-cylindrical members 43, 43 arelinked and secured to the attachment brackets 33, 33 in a state in whichthe respective edges are positioned against each other.

[External Air Introduction Section]

As described above, the exhaust pipe 21 is configured so as to comprisethe bending section 22 at an intermediate position so that the directionin which the exhaust gas is discharged is changed from the horizontaldirection to the vertical direction. The external air introductionsection 50 for taking external air into the external air pathway r inthe downstream-side exhaust pipe 24 that is positioned furtherdownstream of the bending section 22 is installed near the bendingsection 22.

The external air introduction section 50 introduces external air intothe pathway r formed between the downstream-side guide pipe 32 and thedownstream-side protective pipe 42 positioned so that a spacing ispresent with respect to the outer periphery of the downstream-side guidepipe 32. As shown in FIG. 8, the lower-end side of the downstream-sideprotective pipe 42 is extended further downwards than the location atwhich the bending section 22 of the exhaust guide pipe 30 is present. Anupper-section shielding member 35, which forms a part of the shieldingmember described further below, is provided at a location near thebending section 22 of the upstream-side guide pipe 31.

The lower-end side of the downstream-side protective pipe 42 is therebyprovided with the external air introduction section 50, in which alower-end edge 42 d of the downstream-side protective pipe 42 and alower-end edge 35 a of the upper-section shielding member 35 form adownward-opening air intake 51, the external air introduction section 50being configured so that external air is taken in from the air intake51.

As shown in FIGS. 4 and 8, the upper-section shielding member 35 issecured to the inside of the upstream-side protective body 41 at aposition near the bending section 22 of the upstream-side guide pipe 31.

Specifically, the upper section of the upper-section shielding member 35has formed thereon a U-shaped opening that can be fitted from below theupstream-side guide pipe 31. In a state in which this U-shaped openingis fitted so as to be in contact with the front and rear lateral sidesections and the lower section of the upstream-side guide pipe 31, theupper end of the U-shaped opening is in contact with the upper sectionof the inner surface of the upstream-side guide pipe 31, and the lateralside edges of the upper-section shielding member 35 are positionedagainst the inner surface at the front and rear of the upstream-sideguide pipe 31.

In this state, an attachment piece 35 b provided consecutively on thelateral side section of the upper-section shielding member 35, and thefront and rear lateral side portions of the upstream-side protectivebody 41 are detachably linked and secured by a linking bolt 54.

In the external air introduction section 50, the downstream-sideprotective pipe 42 extending further downwards than the location atwhich the bending section 22 of the exhaust guide pipe 30 is present,and the upper-section shielding member 35 form a space s in which theexhaust guide pipe 30 and the bending section 22 thereof are notpresent, the space s being between the bending section 22 of the exhaustguide pipe 30 and the air intake 51. As a result, an air intake path, inwhich narrowing of the flow path by the presence of the exhaust guidepipe 30 or the bending section 22 thereof does not occur, is formed inthe external air introduction section 50; and external air can beintroduced in a smooth manner into the pathway r formed between thedownstream-side guide pipe 32 and the downstream-side protective pipe42.

A lower-section shielding member 52 extending considerably furtherdownwards than the air intake 51 is linked by a linking bolt 53 to thelower-end side of the upper-section shielding member 35 positionedagainst the inner-surface side of the upstream-side protective body 41.

The lower-section shielding member 52 comprises a shielding surface 52 adisposed along the extension direction of the surface of theupper-section shielding member 35 that is disposed along the verticaldirection, and side-shielding surfaces 52 b positioned on both front andrear sides of the air intake 51. A state is obtained in which shieldingis present in three directions excluding the outward side in the lateraldirection of the vehicle body, external air can readily move in from thedownward side and the outward side in the lateral direction of thevehicle body, and hot air from the engine 8 is restricted from enteringthe side towards the air intake 51 from the vehicle-body-interior sidewhere the engine 8 is present.

The upper-section shielding member 35 and the lower-section shieldingmember 52 form a shielding member for minimizing the flow of hot airfrom the side towards the engine 8 to the side towards the external airintroduction section 50.

The downward extension of the lower-section shielding member 52 is setto dimensions at which hot air from the engine 8, which has been guidedby the presence of the channel-shaped upstream-side protective body 41to the vicinity of the air intake 51, is prevented from flowing aroundthe lower end of the lower-section shielding member 52 and reaching theair intake 51 even if some of the hot air flows outwards with respect tothe vehicle body in the course of the hot air leaking out and risingfrom the open lower-edge side of the upstream-side protective body 41.

[Exhaust Section]

The exhaust section 25, which also functions as an ejector section forsuctioning and introducing external air between the outer periphery ofthe downstream-side guide pipe 32 and the inner periphery of thedownstream-side protective pipe 42 by an ejector effect caused byexhaust discharged from the terminal-end opening 32 c of thedownstream-side guide pipe 32, is provided to the downstream-side endsection of the exhaust pipe 21.

Specifically, as shown in FIGS. 3, 4, 9A, and 9B, the exhaust section 25is configured so that: the curved-pipe portion 42 b of thedownstream-side protective pipe 42 comprising an elbow pipe that isexternally fitted to the upper end section of the straight-pipe-shapedcover portion 42 a of the downstream-side protective pipe 42 isprovided, in a state of enclosing the outer periphery side of thecurved-pipe portion 32 b positioned in a continuing manner on the upperend section of the straight-pipe portion 32 a of the downstream-sideguide pipe 32 provided upright so as to have a cylinder axial center ydisposed in the vertical direction, to the outside of the curved-pipeportion 32 b; and the external air pathway r is present between theouter periphery side of the curved-pipe portion 32 b of thedownstream-side guide pipe 32 and the inner periphery side of thecurved-pipe portion 42 b of the downstream-side protective pipe 42.

The terminal-end opening 32 c, which is at the downstream-side endsection of the curved-pipe portion 32 b positioned in a continuingmanner on the upper end section of the straight-pipe portion 32 a of thedownstream-side guide pipe 32, is positioned further upstream than theposition of a terminal opening 42 c positioned at the downstream-sideend section of the curved-pipe portion 42 b of the downstream-sideprotective pipe 42. Exhaust emitted from the terminal-end opening 32 cof the downstream-side guide pipe 32 is thereby discharged whileexternal air present in the external air pathway r on the outerperiphery side of the downstream-side guide pipe 32 is suctioned andguided out. Flow of external air is generated by an ejector effect inthe external air pathway r between the outer periphery side of thedownstream-side guide pipe 32 and the inner periphery side of thedownstream-side protective pipe 42, and the downstream-side guide pipe32 can be cooled up to the terminal-end opening 32 c.

In the exhaust section 25, the spacing between the outer peripheryposition of the downstream-side end section of the curved-pipe portion32 b of the downstream-side guide pipe 32 and the inner peripheryposition of the downstream-side end section of the curved-pipe portion42 b of the downstream-side protective pipe 42, i.e., the width of theexternal air pathway, is set as shown in FIGS. 9A and 9B.

Specifically, as regards the spacing between the outer peripheryposition of the downstream-side end section of the curved-pipe portion32 b of the downstream-side guide pipe 32 and the inner peripheryposition of the downstream-side end section of the curved-pipe portion42 b of the downstream-side protective pipe 42, the positionalrelationship between the curved-pipe portion 32 b of the downstream-sideguide pipe 32 and the curved-pipe portion 42 b of the downstream-sideprotective pipe 42 is set so that the pathway width L2 in the upper sidefurther from the respective centers of curvature o1, o2 of thecurved-pipe portions 32 b, 42 b is greater than the pathway width L1 inthe lower side nearer the centers of curvature o1, o2.

Here, when viewed from each of the terminal-end openings 32 c, 42 calong the exhaust direction (see line segments p1, p2 shown in FIG. 9A),the relative positions of each of the curved-pipe portions 32 b, 42 bhaving a circular cross-section profile are set so that the center pointp1 (located on line segment p1 shown in FIG. 9A and therefore indicatedby the same numeral) of the terminal-end opening 32 c of thedownstream-side guide pipe 32 is located further downward, nearer therespective centers of curvature o1, o2 of the curved-pipe portions 32 b,42 b, than the center point p2 (located on line segment p2 shown in FIG.9A and therefore indicated by the same numeral) of the terminal opening42 c of the downstream-side protective pipe 42, as shown in FIG. 9B.

It is assumed that, in cases in which the terminal-end opening 32 c ofthe downstream-side guide pipe 32 is located at the same position as thecenter point p2 of the terminal opening 42 c of the downstream-sideprotective pipe 42 as shown by the imaginary lines in FIG. 9A,high-temperature exhaust gas is discharged from the terminal-end opening32 c of the downstream-side guide pipe 32 into a vertically orienteddischarge region within a range indicated in the drawing by dashedtwo-dotted lines u2, d2. In such an instance, there is a possibilitythat the upper-end side location of the discharge region indicated bythe upper dashed two-dotted line u2 will come into contact with theupper side of the terminal opening 42 c of the downstream-sideprotective pipe 42.

In contrast, in cases in which the center point p1 of the terminal-endopening 32 c of the downstream-side guide pipe 32 is located furtherdownwards and nearer the centers of curvature o1, o2 than the centerpoint p2 of the terminal opening 42 c of the downstream-side protectivepipe 42 as shown by a solid line in FIG. 9A, it is assumed that thehigh-temperature exhaust gas discharged from the terminal-end opening 32c of the downstream-side guide pipe 32 will be discharged into avertically oriented discharge region within a range indicated in thedrawing by dashed two-dotted lines u1, d1. In such an instance, it ispossible to reduce the possibility of a part of the upper dotted line u1coming into contact with the upper side of the terminal opening 42 c ofthe downstream-side protective pipe 42.

In the above embodiment, a diesel engine comprising the exhaust cleaningtreatment device 20 with a muffler function accommodating a dieseloxidation catalyst (DOC) and a diesel particulate filter (DPF) isemployed as the engine 8. However, [the present invention] is notlimited thereto, and can be applied to an exhaust device for a workvehicle in which a gasoline engine is employed.

Other structures may be configured in a similar manner to that in theembodiment described above.

In the above embodiment, a sheet-shaped insulating material obtained byforming an aluminum corrugated material and imparting heat-proofing andsound-proofing functions thereto is used as the sheet-shaped insulatingmaterial 41 b provided to the inner surface side of the externalprotective pipe 40. However, [the present invention] is not limitedthereto, and any appropriate insulating material can be employed. Aconfiguration is also possible in which no insulating material is used.

Other structures may be configured in a similar manner to that in theembodiment described above.

In the above embodiment, the curved-pipe portion 42 b of thedownstream-side protective pipe 42 is configured using a member separatefrom the straight-pipe-shaped cover portion 42 a, and is provided with aheat-resistant coating applied to the inner periphery side. However,[the present invention] is not limited thereto; for example, thefollowing configuration is also possible.

For example, the curved-pipe portion 42 b may be integrally configuredwith the straight-pipe-shaped cover portion 42 a, and a heat-resistantcoating may be applied to the inner periphery side of the curved-pipeportion 42 b where the sheet-shaped insulating material 44 is notattached; the curved-pipe portion 42 b configured using a memberseparate from the straight-pipe-shaped cover portion 42 a may be madefrom a heat-resistant material; heat-resistant coating may further beapplied to the curved-pipe portion 42 b made from a heat-resistantmaterial and configured using a separate member, or similar means may beimplemented.

Other structures may be configured in a similar manner to that in theembodiment described above.

In the above embodiment, the curved-pipe portion 32 b of thedownstream-side guide pipe 32 and the curved-pipe portion 42 b of thedownstream-side protective pipe 42 are configured using curved-pipeportions 32 b, 42 b, each of which having a circular cross-sectionprofile. The positions of the respective center points p1, p2 of theterminal-end openings 32 c, 42 c are displaced along the verticaldirection, whereby the widths L1, L2 of the external air pathway rformed between each of the curved-pipe portions 32 b, 42 b are made todiffer above and below the curved-pipe portion 32 b of thedownstream-side guide pipe 32.

In other words, the positional relationship between the curved-pipeportion 32 b of the downstream-side guide pipe 32 and the curved-pipeportion 42 b of the downstream-side protective pipe 42 is set so thatthe pathway width L2 in the upper side further from the respectivecenters of curvature o1, o2 of the curved-pipe portions 32 b, 42 b isgreater than the pathway width L1 in the lower side nearer the centersof curvature o1, o2. However, [the present invention] is not limitedthereto; for example, one or both of the curved-pipe portions 32 b, 42 bmay have an elliptical or a similarly shaped cross-section so that thewidths L1, L2 of the external air pathway r formed between thecurved-pipe portions 32 b, 42 b differ above and below the curved-pipeportion 32 b of the downstream-side guide pipe 32.

In the above embodiment, an example is given for a structure in whichthe lower-section shielding member 52 of the external air introductionsection 50 is supported by the upper-section shielding member 35provided near the bending section 22 of the upstream-side guide pipe 31.However, the structure for supporting the lower-section shielding member52 is not limited to that shown. For example, support may be provided bythe upstream-side protective body 41, the downstream-side protectivepipe 42, or at another appropriate location, as long as the structuredoes not block introduction of external air from the air intake 51 andis capable of minimizing the flowing around of hot air from the sidetowards the engine 8. It is also possible to omit the lower-sectionshielding member 52. Also, support of the upper-section shielding member35 may be provided not only by the upstream-side protective body 41 butalso by the upstream-side guide pipe 31 or at another appropriatelocation.

The upper-section shielding member 35 and the lower-section shieldingmember 52 are not limited to those configured using different members,and may be integrally formed using a single member, or formed as acombination of three or more separate members.

Other structures may be configured in a similar manner to that in theembodiment described above.

In the above embodiment, the exhaust pipe portion 20 a of the exhaustcleaning treatment device 20 is equipped with the flow-regulating plates26. However, [the present invention] is not limited thereto. Forexample, the interior of the exhaust pipe portion 20 a may be equippedwith a mesh filter comprising a large number of vent holes, or anotherstructure may be provided in which it is easy to avoid the occurrence ofcavitation generated by a vortex of exhaust accompanying a boost inacceleration during excess load. The flow-regulating plates 26, the meshfilter, or another such structure for avoiding the occurrence ofcavitation may also be omitted.

Other structures may be configured in a similar manner to that in theembodiment described above.

The exhaust device for a work vehicle according to the present inventioncan be applied not only to a tractor but also to a combine harvester orother mobile agricultural machinery; an excavator or other type ofbuilding machinery or construction machinery; a goods transportationvehicle; or other work vehicles.

What is claimed is:
 1. An exhaust device for a work vehicle comprising:an exhaust pipe for guiding exhaust to a vehicle exterior, the exhaustpipe including: an exhaust guide pipe into which exhaust from an engineis introduced; an external protective pipe that externally fits onto theexhaust guide pipe and forms a passage for external air in a spacebounded on one side by the exhaust pipe; and an ejector section forsuctioning and introducing external air between an outer periphery ofthe exhaust guide pipe and an inner periphery of the external protectivepipe by an ejector effect caused by exhaust discharged from the exhaustguide pipe, the ejector section being formed on a downstream-side endsection of the exhaust pipe by positioning a downstream-side end sectionof the external protective pipe further downstream, with respect to anexhaust direction, than a downstream-side end section of the exhaustguide pipe; wherein: a curved-pipe portion curved so as to change theexhaust direction is connected to the downstream-side end section ofeach of the exhaust guide pipe and the external protective pipe,respectively, and spacing between an end-section outer periphery of theexhaust guide pipe and an end-section inner periphery of the externalprotective pipe in the curved-pipe portions is greater on a sideopposite the center of curvature of the respective curved-pipe portionsthan the side nearer the center of curvature.
 2. The exhaust device fora work vehicle according to claim 1, wherein a terminal-end opening onthe downstream-side of the exhaust guide pipe and a terminal-end openingon the downstream-side of the external protective pipe are provided sothat, when viewed along the exhaust direction from the terminal-endopening, a center point of the terminal-end opening of the exhaust guidepipe is positioned nearer the center of curvature of the curved-pipeportion connected to the exhaust guide pipe than the center point of theterminal-end opening of the external protective pipe.
 3. The exhaustdevice for a work vehicle according to claim 1, wherein the curved-pipeportions of the exhaust guide pipe and the external protective pipe areeach configured using a curved member that is separate from the externalprotective pipe and the exhaust guide pipe.
 4. The exhaust device for awork vehicle according to claim 1, wherein a heat-resistant coating isapplied to the curved-pipe portions of the exhaust guide pipe and theexternal protective pipe.
 5. The exhaust device for a work vehicleaccording to claim 1, wherein a terminal-end opening of the curved-pipeportion of the exhaust guide pipe is positioned further upstream than aterminal opening of the curved-pipe portion of the external protectivepipe.